1. Field of the Invention
This invention relates to a concentrator for focusing sunlight onto a central receiver by means of mirrors revolving around the receiver. Central-receiver concentrators can be used to produce the high-pressure steam needed in power plants.
2. Discussion of the Prior Art
Sunlight can replace coal, natural gas, or uranium as the source of energy for electric power plants. Sunlight must be collected and concentrated to obtain the high temperature needed for producing high-pressure steam used in power plants. Several high-pressure steam solar power plants were built in the 1970's and early 1980's. They proved to be much too expensive and inefficient for widespread commercial use.
The high cost and poor performance of the plants was attributed to the heliostats used as solar concentrators. Heliostats include massive steel and concrete pedestals supporting mirrors that rotate about 2 axes to keep sunlight focused on a central receiver. Mirrors mounted on pedestals are inherently expensive and inefficient. Each heliostat requires 2 sets of precise hinges, motors, and gearboxes to rotate the mirrors about 2 axes. The mirrors cannot rotate about the receiver to keep facing the sun, or move out of shadows of other mirrors, or move out of storms. When these earlier plants were built there were no suitable mobile-mirror solar concentrators.
Solar energy concentrators focusing sunlight onto a central receiver by means of mirrors revolving around a central receiver are known in my U.S. Pat. No. 5,787,878 which shows a mobile-mirror solar energy concentrator with mirrors rotated by hydraulic pistons linked with hydraulic hoses to a few motors and pumps on each train. The trains are braced against wind with cables anchored to moving trains. When storms threaten, the cables are reeled in with rack and pinion drives as the trains move to closely-spaced tracks where the trains are nested compactly and enclosed by roof panels attached to the mirrors. One disadvantage is the cost of the large number of pistons, hoses, cable reels, and rack and pinion drives required. Another disadvantage is the amount of land and track required. Still another disadvantage is the weight and complexity of roof panels attached to the mirrors.